Development of Metabolically Active Linkers (MALs) to Improve Diagnostic and Radiotherapeutic HPMA Copolymers

目标： 诊断性和治疗性纳米医学进步的主要障碍是由药物递送系统在与单核吞噬细胞系统相关的器官（特别是肝脏和脾脏）中的积累引起的非靶向滞留。该提案的重点是开发177 Lu-DOTA-代谢活性接头（MAL），其显著降低诊断和放射性HPMA共聚物的非靶标保留，从而导致肿瘤与非靶标比率的增加。我们建议设计和开发在组织蛋白酶B和S存在下酶促切割的MAL，已知组织蛋白酶B和S在肝脏和脾脏中高度表达。MAL的裂解将产生低分子量放射性代谢物，预期其可更有效地从非靶组织中清除，同时仍在肿瘤中实现显著保留。对于治疗应用，这种增强的从非靶组织的清除将显著降低非靶毒性。如果成功的话，MAL策略将很容易整合到各种各样的纳米医学平台中，以大大提高这些药物治疗癌症和其他疾病的疗效和转化潜力。 研究设计：本提案的第一个目的是合成、纯化、表征和放射性标记177 Lu-DOTA-MAL-HPMA共聚物。合成试剂后，将在人巨噬细胞和HPAC胰腺癌细胞系中研究试剂的内化、外排和代谢特性。该提案的第二个目的将集中于177 Lu-DOTA-MAL-HPMA共聚物的初始体内评价。这些研究将包括生物分布、人体剂量估计、体内代谢和microSPECT/CT成像研究。最后，第三个目的将评估177 Lu-DOTA-MAL-HPMA共聚物单独和与当前胰腺癌化疗方案组合的治疗潜力。作为治疗评价的一部分，将进行最大耐受剂量测定和组织病理学分析，以评估疗效和毒性。

Objective: A major barrier to the advancement of diagnostic and therapeutic nanomedicines has been the non-target retention caused by the accumulation of the drug delivery systems in organs associated with the mononuclear phagocyte system, particularly the liver and spleen. The focus of this proposal is on the development of 177Lu-DOTA-Metabolically Active Linkers (MALs) that substantially reduce the non-target retention of diagnostic and radiotherapeutic HPMA copolymers, thereby leading to an increase in the tumor to- non-target ratios. We propose to design and develop MALs that enzymatically cleave in the presence of Cathepsins B and S, which are known to be highly expressed in the liver and spleen. Cleavage of the MALs will generate low molecular weight radiometabolites which are expected to clear more effectively from nontarget tissue while still achieving significant retention in tumors. For therapeutic applications, this enhanced clearance from non-target tissues will substantially decrease non-target toxicity. If successful, the MAL stratagem will be easily integrated into a wide variety of nanomedicine platforms to substantially enhance the efficacy and translational potential of these agents for treating cancer and other diseases. Study Design: The first aim of this proposal is to synthesize, purify, characterize and radiolabel the 177Lu- DOTA-MAL-HPMA copolymers. Upon synthesizing the agents, the intemalization, efflux and metabolism properties of the agents will be investigated in human macrophage and the HPAC pancreatic cancer cell line. The second aim of the proposal will focus on the initial in vivo evaluation of the 177Lu-DOTA-MAL-HPMA copolymers. These studies will include biodistribution, human dose estimation, in vivo metabolism and microSPECT/CT imaging studies. Lastly, the third aim will evaluate the therapeutic potential of the 177Lu- DOTA-MAL-HPMA copolymers alone and in combination with current pancreatic cancer chemotherapeutic regimens. As part of the therapeutic evaluation, maximum tolerated dose determinations and histopathological analysis will be performed to gauge therapeutic efficacy and toxicity.